Apparatus for producing ions of vaporizable materials



Jan. 28, 1958 B. T. WRIGHT 2,321,632

APPARATUS FOR PRODUCING IONS 0F VAPORIZABLE MATERIALS Filed Sept. 25, 1944 2 Sheets-Sheet 1 SUPPLY HEATER SUPPLY FILAMENT SUPPLY ACCELER ATING ELECTRODE SUPPLY MAGNETIC FIELD 1 IONIZING ELECTRONS IONS TO COLLECTOR as COLLIMATING ELECTRODE CATHODE 5 OLLIMATING ELECTRODE a ONS TO COLLECTOR lomzmc; ELECTRONS ANODE ARC SUPPLY L 88 INVENTOR. V. a. YRON 7.' WRIGHT :6 A BY Q M444 ATTORNEY.

' Jan. 28, 1958 B. T. WRIGHT APPARATUS FOR PRODUCING IONS OF VAPORIZABLE MATERIALS 2 Sheets-Sheet 2 Filed Sept. 25, 1944 INVENTOR. BYRON 7T WRIGHT ATTORNEY.

102 s? BY APPARATUS FOR PRODUCING IONS OF VAPORIZABLE MATERIALS Byron T. Wright; Berkeley, Calif., assignor-to the United States of America as represented by the United States Atomic Energy Commission Application September 25, 1944,- Serial No. 555,615

13 Claims. (Cl. 25041.9)

The present invention relates to electric discharge devices, and more particularly to calutron ion sources.

It is an object of the invention to provide an improved ion source having a gaseous region disposed in a magnetic field, with a pair of gas ionizing devices for producing ionization along an extended line aligned with the magnetic field.

Another object of the invention is to provide an improved ion source having a gaseous region disposed in a magnetic field with an electron source in the region, and means for projecting electrons from the source into the gaseous region in opposite directions along the magnetic field to produce two collinear arc discharges.

A further object of the invention is to provide an electric discharge device having a gaseous region disposed in a magnetic field and an electron source in the region with means for projecting two beams of electrons of welldefined cross section in opposite directions along the magnetic field to produce a pair of collinear are discharges in the gaseous region.

A further object is to provide a calutron with an improved ion source having an electrode arrangement productive of a uniform and copious supply of ions.

A still further object is to provide an improved ion source unit with an electrode arrangement of rugged construction.

The invention, both as to its organization and method of operation, together with other objects and advantages thereof, will best be understood by reference to the following specification taken in connection with the accompanying drawings, in which Figure 1 is a diagrammatic sectional plan view of a calutron, taken along the line 1-1 in Fig. 2, incorporating an ion source unit embodying the present invention; Fig. 2 is a diagrammatic sectional elevational view of the calutron taken along the line 2-2 in Fig. 1; Fig. 3 is a schematic perspective view of the electrode arrangement incorporated in the ion source unit of the calutron; Fig. 4 is a longitudinal sectional view of the calutron ion source unit, illustrating the structure thereof; Fig. 5 is a front elevation view of the ion source unit shown in Fig. 4; and Fig. 6 is a sectional view of the ion source unit, taken along the line 6-6 of Fig. 4.

At the outset, it is noted that a calutron is a machine of the character of that disclosed in the copending application of Ernest 0. Lawrence, Serial No. 557,784, filed October 9, 1944, now U. S. Patent No. 2,709,222, and is employed to separate the constituent isotopes of an element and, more particularly, to increase the proportion of a selected isotope in an element containing several isotopes in order to produce the element enriched with the selected isotope. For example, the machine is especially useful in producing uranium enriched with 235 Such a calutron essentially comprises means for vaporizing a quantity of material containing an element that is to be enriched with a selected one of its several isotopes; means for subjecting the vapor to ionization, whereby at least a portion of the vapor is ionized causing 2,821,632 Patented Jan. as, 1958 "ice ions of the several isotopes of the element tobe produced; electricalmeans for segregating the ions from the unionized vapor and for accelerating the segregated ions to relatively high velocities; electromagnetic means for deflecting the ionsalong curved paths, the radii of curvature of the paths of the ions being proportional to the square roots of the masses of the ions, whereby the ions are concentrated in accordance with their masses; and means for de-ionizing and collecting the ions of the selected isotope thus concentrated, thereby to produce a deposit of the element enriched with the selected isotope.

In accordance with the present invention, an improved ion source is provided in which electrons are projected into the vapor-containing region of the arc-block as two collinear streams, whereby the electrons encounter and ionize molecules of the vapor introduced into said region. Preferably, the ion source comprises a single thermionically emissive cathode disposed intermediate the ends of the vapor-containing region, cooperating with an arrangement of electrodes for projecting electrons from the cathode in opposite directions along the magnetic field extending through the vapor-containingregion. In the preferred embodiment, anodes are arranged on opposite sides of the thermionically emissive cathode in line therewith along the magnetic field, anda pair of apertured electrodes are disposed respectively also on opposite sides of the cathode, adjacent thereto, andbetween the cathode and the respective anodes. The dimensions of the cathode and the openings in the apertured electrodes are proportioned to define arc discharges of uniform cross section throughout the discharges lengths. The cathode and the openings in the apertured electrodes and anodes are substantially in alignment with the magnetic field extending through the aforesaid vapor-containing region. With such an electrode arrangement, a pair of arc discharges of uniform cross sections are produced in, the vapor-containing region, and the regions of ionization in which these arc discharges are effective are of an extended. length and of substantially uniform cross section throughout. Therefore when such an ion source is used in a calutron, an arc of effectively increased length is obtained, and the eificiency and economy of commercial calutron operation is increased.

Referring now more particularly to Figs. 1 and 2 of the drawings, there is illustrated a calutron provided with an ion source embodying the features of the present invention. The calutron 10 comprises magnetic field structure including upper and lower pole pieces 11 and 12, provided with substantially flat parallel spaced-apart pole faces, and a tank 13, disposed between the pole faces of the pole pieces 11 and 12. The pole pieces 11 and 12 carry windings, not shown, which are adapted to be energized in order to produce a substantially uniform and relatively strong magnetic field therebetween, which mag netic field passes through the tanl; 13 and the various parts honsed therein. The tank 13 is of tubular configuration, being substantially U- or crescent-shaped in plan, and comprising substantially flat parallel spacedapart top and bottom walls 14 and 15, upstanding curved inner and outer side walls 16 and 17, and end walls 18 and 19. The end walls 18 and 19 close the opposite ends of the tubular tank and are adapted to be removably secured in place, whereby the tank 13 is hermetically sealed. Also, vacuum pumping apparatus 13a is associated with the tank 13, whereby the interior of the tank 13 may be evacuated to a pressure of the order of 10- 10 mm. Hg. Preferably, the component parts of the tank 13 are formed of steel, the top and bottom walls 14 and 15 thereof being spaced a short distance from the pole faces of the upper and lower pole pieces 11 and 12, respectively, the tank 13 being retained in such position in any suitable manner, whereby the top and bottom walls l4 and 15 constitute in elfect pole pieces with .3. respect to the interior of the tank 13, as explained more fully hereinafter.

The removable end wall 18 suitably supports an ion source unit 20 comprising a charge receptacle 21 and a communicating arc-block 22. An electric heater 23 is arranged in heat exchange relation with the charge receptacle 21 and is adapted to be connected to a suitable source of heater supply, whereby the charge receptacle 21 may be appropriately heated, the charge receptacle 21 being formed of steel or the like. The arc-block 22 is formed, at least partially, of carbon or graphite and is substantially C-shaped in plan, being provided with upper and lower collinear upstanding slots 24a and 24b respectively, formed in the front wall thereof remote from the charge receptacle 21. Thus, the arc-block 22 is of hollow construction, the cavity therein communieating with the interior of the charge receptacle 21 and with the tank.

The ion source unit is provided with a filamentary cathode 25 adapted to be connected to a suitable source of filament supply, the filamentary cathode 25 being disposed within the cavity formed in the arc-block 22 and approximately halfway between the ends thereof between the two upstanding slots 24a and 24b. The ion source unit also is provided with a pair of anodes 27 and 28, the upper anode 27 being disposed substantially at the upper end of the arc-block 22 to define the upper end of the slot 24a and the lower anode 28 being disposed substantially at the lower end of the arc-block 22 to define the lower end of the slot 24b. Further, the ion source unit includes a pair of apertured collimating electrodes 29 and 30, respectively disposed on opposite sides of the cathode 25 and adjacent thereto substantially within the cavity formed in the are-block 22, the upper collimating electrode 29 being disposed at the lower end of the upper slots 24a, and the lower collimating electrode 30 being disposed at the upper end of the lower slot 24b. The respective collimating electrodes 29 and 30 have elongated transversely extending collirnating slots 31 and 32 therethrough, said slots being aligned with the filamentary cathode 25 across the magnetic field 33. The anodes 27 and 28, the eollimating electrodes 29 and 30, thearc-block 22 and charge receptacle 21 are electrically connected to the positive terminal of the arc current supply and grounded. Likewise, the tank 13 is grounded. Also, the filamentary cathode 25 is connected to the negative terminal of the aforesaid source of arc current supply. Further, the removable end wall 18 carries an acceleratmg structure 37 formed of carbon or graphite, and disposed in spaced-apart relation with respect to the front wall of the arc-block 22 in which the slots 24a and 24b are formed. A slit 38 is formed in the ion accelerating electrode 37 and arranged in substantial alignment with respect to the slots 24a and 24b formed in the wall of the arc-block 22. A suitable source of accelerating electrode potential supply is adapted to be connected between the arc block 22 and the ion accelerating electrode 37, the positive and negative terminals of the potential supply source being connected to the arc-block 22 and to the m accelerating electrode 37, respectively. Further, the positive terminal of the ion accelerating electrode potential supply is grounded.

The removable end wall 19 suitably supports a collector block 39 formed of stainless steel or the like and provided with two laterally spaced-apart cavities or pockets 40 and 41, which respectively communicate with slots 42 and 43 formed in the front wall of the collector block 39 disposed remote from the removable end wall 19. It 1s noted that the pockets 40 and 41 are adapted to receive two constituent isotopes of an element which have been separated in the calutron 10, as explained more fully hereinafter. Further, the inner wall 16 suitably supports a tubular liner 44 formed of copper or the like, rectangular in vertical transverse cross section, disposed within the tank 13 and spaced from the walls 14, 15, 16, and 17. One end of the tubular liner 44 is positioned adjacent the accelerating electrode structure 37 and the other end is disposed adjacent the collector block 39; the tubular liner 44 functions as an electrostatic shield for the high velocity ions traversing the curved paths between the slit 38 formed in the ion accelerating electrode structure 37 and the slots 42 and 43 formed in the collector block 39, as explained more fully hereinafter. Finally, the tubular liner 44 is electrically connected to the ion accelerating structure 37 and to the collector block 39. Thus, it will be understood that the ion source unit 20 and the tank 13 are connected to the grounded positive terminal of the accelerating electrode potential supply; while the ion accelerating electrode structure 37, the tubular liner 44, and the collector block 39 are connected to the ungrounded negative terminal of the accelerating electrode potential supply; the ion accelerating electrode structure 37, the tubular liner 44, and the collector block 39 being electrically insulated from the tank 13 and the ion source unit 20.

Referring now more particularly to Fig. 3 of the drawings, the electrode arrangement of the calutron ion source 20 embodying the features of the present invention is illustrated schematically in perspective. More particularly, this electrode arrangement comprises, among other elements, a straight filamentary cathode 25, formed of tungsten, tantalum or the like, a pair of apertured platelike collimating electrodes 29 and 30 formed of tungsten, molybdenum or the like, positioned on opposite sides of the filamentary cathode 25, and a pair of anodes 27 and 28 positioned on opposite sides of the plate-like collimating electrodes 29 and 30 and at distances therefrom relatively large compared to the distances from the fila' mentary cathode 25 to the collimating electrodes 29 and 30. The electrodes mentioned are arranged in the magnetic field of the calutron, the direction of the field between the north pole and the south pole of the field structure being indicated by the arrow 33. The anodes 27 and 28 are arranged in substantially parallel longitudinal spaced-apart relation and are positioned with the major faces thereof transverse to the magnetic field mentioned; the collimating electrodes 29 and 30 are arranged between the anodes 27 and 28 in substantially parallel relation therewith and also disposed with the major faces thereof transverse to the magnetic field mentioned. The collimating electrodes 29 and 30 have elongated collimating slots 31 and 32 formed therethrough, said slots being disposed parallel to the central portion of the filamentary cathode 25 disposed between said collimating electrodes. Accordingly, the filamentary cathode 25, the collimating electrodes 29 and 30, and the anodes 27 and 28 are respectively disposed in five substantially parallel planes, spaced apart longitudinally and disposed substantially normal to the magnetic field mentioned. Furthermore, the central portion of the filamentary cathode 25 and the slots 31 and 32 formed in the collimating electrodes 29 and 30 are arranged in alignment with the magnetic field mentioned.

The slots 31 and 32 formed in the collimating electrodes 29 and 30 are narrower than the central portion of the filamentary cathode 25. Furthermore these slots are shorter than the filamentary cathode in the direction along the length of the filament 25, whereby the dimensions of said slots are less than the corresponding dimensions of the filamentary cathode 25. Thus, an ion source is provided .having a central cathode and an arrangement of electrodes symmetrically disposed on opposite sides of the cathode for projecting ionizing electrons in opposite directions as two collinear beams into a region containing vapor to be ionized.

The filamentary cathode 25 is electrically connected by way of an adjustable resistor 45 to a corresponding source of filament-current supply indicated as a battery 48. The

filamentary cathode 25 is connected to the negative termi-.

nal of the arc current supply; and the anodes 27 and 28 are connected .to the positive terminal of said arc current supply. The collimating electrodes 29 and 30 are electrically connected to the anodes 27 and 28, and to the arc-block 22 as previously noted, whereby upper and lower substantially electric-fieldfree zones 46 and 47 are defined in the gaseous region formed by the cavity in the arc-block 22, the upper electric-field-free zone 46 being between the upper collimating electrode 29 and the upper anode 27, and the lower electric-field-free zone 47 being formed between the lower collimating electrode 34) and the lower anode 28.

Considering now the general principle of operation of the calutron .10 shown in Figs. 1 and 2 incorporating the ion source unit illustrated, a charge comprising a compound of the element to be treated is placed in the charge receptacle 21, the compound of'the element mentioned being one which may be readily vaporized. The end walls 18 and 19 are securely attached to the open ends of the tank 13 and the tank is hermetically sealed. The various electrical connections are completed and operation of the vacuum pumping apparatus 13a associated with the tank 13 is initiated. When a pressure of the order of to 10- mm. Hg is established within the tank 13, the electric circuits for the windings, not shown, associated with the pole pieces 11 and 12 are closed and adjusted, whereby a predetermined magnetic field is established therebetween traversing the tank 13. The electric circuit for the heater 23 is closed, so that the charge in the charge receptacle 21 is heated and vaporized. The vapor fills the charge receptacle 21 and is conducted into the communicating cavity formed in the arc-block 22 and into the two zones 46 and 47 mentioned. The electric circuit for the filamentary cathode 25 is closed, whereby the filamentary cathode 25 is heated and rendered electron emissive. Then, the electric circuit between the fil amentary cathode 25 and the arc-block 22 is closed, rendering the filamentary cathode 25 negative with respect to the collimating electrodes 29 and 30 and to the anodes 27 and 28 and to the arc-block 22. Accordingly, electrons are projected from the filamentary cathode 25 in opposite directions toward the corresponding collimating electrodes 29 and 38 along the magnetic field. Some of these electrons pass through the slots 31 and 32 formed in the collimating electrodes 29 and 30 and continue into the two substantially electric-field-free zones 46 and 47 in the cavity formed in the arc-block 22 between the collimating electrodes 29 and 30 and the respective adjacent anodes 27 and 28, whereby the gas or vapor in the zones 46 and 47 in the cavity formed in the arc-block 22 on opposite sides of the filamentary cathode 25, is ionized. The electrons proceeding from the filamentary cathode 25 through the collimating slots 31 and 32 in the collimating electrodes 29 and 30 encounter molecules of the vapor in the two zones 46 and 47 or" the cavity formed in the arc-block 22 and break up the molecular form of the compound of the vapor to a considerable extent, producing positive ions of the element that is to be enriched with the selected one of its isotopes.

More specifically, the electrons projected from the filam'entary cathode 25 gain substantially all of their energy in traversing the electric field between the filamentary cathode 25 and the two collimating electrodes 29 and 30, whereby they enter the two zones 46 and 47 in the gaseous or vapor region in the cavity formed in the arc-block 22 at velocities sutficient to produce ionization of the gas, or vapor. Moreover, the electrons traveling into the vapor region through the collimating slots 31 and 32 are, for the most part, confined to paths along the magnetic field, inasmuch as any horizontal motion imparted to these electrons will result in their traveling along helices of extremely small radii, the axes of the helices being substantially along the magnetic field.

In view of the fact that the dimensions of the slots 31 and 32 formed in the collimating electrodes 29 and 3.0 are less than the corresponding dimensions of the filamentary cathode 25, the cross sections of the electron streams entering the zones 46 and 47 of the gaseous region respectively disposed between the collimating electrodes 29 and 30 and the corresponding adjacent anodes 27 and 28 are positively defined, and only electrons from the uniform electron-emissive surface of the central portion of the filamentar-y cathode 25 are employed. These uniform and steady streams of electrons projected into the zones 46 and 47 of the gas or vapor region mentioned result in a pair of arc discharges therethrough along the magnetic field and opposite the slots 24a and 24b formed in the front wall of the arc-block 22, whereby a uniform and copious supply of positive ions is produced in the two zones 46 and 47 mentioned. Each of these are discharges is characterized by a high current, a low voltage drop, and a luminous plasma. More specifically, most of the electrons projected from the filamentary cathode 25 through the slots 31 and 32 in the collimating electrodes 29 and 30 proceed to the respective anodes 27 and 28, thereby to complete the circuit between the positive and the negative terminals of the arc supply, current in the are discharges flowing from the anodes 27 and 28 to the filamentary cathode 25.

Due to the construction and arrangement of the electrodes of the ion source 20, the streams of electrons proceeding from the filamentary cathode 25 through the slots 31 and 32 formed in the collimating electrodes 29 and 30 form two collinear ribb'orrlike configurations, within the boundaries of which most of the positive ions formed in the gas or vapor region are concentrated. This arrangement produces a uniform and copious supply of positive ions, and these are adapted to be fed to the slots 24a, 24b in the wall of the arc-block 22 with which the ion accelerating structure 37 is operatively associated.

The electric circuit between the arc-block 22 and the ion accelerating structure 37 is then completed, the accelerating structure 37 being at a high negative potential with respect to the arc-block 22, whereby the positive ions in the upper and lower zones 46 and 47 in the arc-block 22 are attracted by the ion accelerating structure 37 and accelerated through the voltage impressed therebetween to form two beams of ions. More particularly, the positive ions proceed from the upper ionization zone 46 in the cavity formed in the arc-block 22, through the upper slot 24a formed in the wall thereof, and across the space between the ion accelerating structure 37 and the adjacent wall of the arc-block 22, and thence through the slit 38 formed in the ion accelerating structure 37 as an upper beam into the interior of the tubular liner 44. Likewise,

the positive ions proceed from the lower ionization zone 47 in the cavity formed in the arc-block 22, through the lower slot 24b formed in the Wall thereof, and across the space between the ion accelerating structure 37 and the adjacent wall of the arc-block 22, and thence through the slit 38 formed in the ion accelerating structure 37 as a lower beam into the interior of the tubular liner 44. When ions in the two beams of high-velocity positive ions pass through the accelerating structure 37, they merge to form a single vertical upstanding beam proceeding from the arc source 20 into the tubular liner 44.

As previously noted, the collector block 39, as well as the tubular liner 44, are electrically connected to the ion accelerating structure 37, whereby there is an electricfield-free path for the high-velocity positive ions disposed between the ion accelerating structure 37 and the collector block 39 within the tubular liner 44. The high-velocity positive ions entering the end of the liner 44 adjacent to the accelerating electrode 37 are deflected from their normal straight-line path and from a vertical plane passing through the center of the slots 24a and 24b, and the center of the aligned slit 38, by the relatively strong magnetic field maintained through the space within the tank 13 and the liner 44 through which the positive ions travel,

7 whereby the positive ions describe arcs, the radii of which are proportional to the square roots of the masses of the ions and consequently of the isotopes of the element mentioned. Thus, ions of a relatively light isotope of the element describe an interior are of relatively short radius and are focused through the slot 42 into the pocket 40 formed in the collector block 39; whereas ions of a relatively heavy isotope of the element describe an exterior are of relatively long radius and are focused through the slot 43 into the pocket 41 formed in the collector block 39. Accordingly, the relatively light ions are collected in the pocket 40 and are de-ionized to produce a deposit of the relatively light isotope of the element therein; while the relatively heavy ions are collected in the pocket 41 and are ,de-ionized to produce a deposit of the relatively heavy isotope of the element therein.

After all of the charge in the charge receptacle 21 has been vaporized, all of the electric circuits are interrupted and the end wall 18 is removed so that another charge maybe placed in the charge receptacle 21 and subsequently vaporized in the manner explained above. After a suitable number of charges have been vaporized in order to obtain appropriate deposits of the isotopes of the element in the pockets 40 and 41 of the collector block 39, the end wall 19 may be removed and the deposits of the collected isotopes in the pockets 40 and 41 in the collector block 39 may be reclaimed.

Of course, it will be understood that the different dimensions of the parts of the calutron 10, the various electrical potentials applied between the electrodes and parts thereof, as well as the strength of the magnetic field between the pole pieces 11 and 12, are suitably correlated with respect to each other, depending upon the mass,

numbers of the several isotopes of the element that is to be treated therein. In this connection, reference is again made to the copending application of Ernest 0. Lawrence, for a complete specification of a calutron especially designed for the production of uranium enriched with the isotope U By way of illustration, it is noted that when the calutron is employed in order to produce uranium enriched with U the compound of uranium which is suggested as a suitable charge in the charge receptacle 21 is UCl as this compound may be readily vaporized and the molecular form of the vapor may be readily broken up to form positive ions of uranium with great facility. In this case, uranium enriched with U is collected in the pocket 40 of the collector block 39 and uranium comprising principally U is collected in the pocket 41 of the collector block 39. Also, it is noted that from a practical standpoint, the deposit of uranium collected in the pocket 40 of the collector block 39 contains considerable amounts of U in view of the fact that this isotope comprises the dominent constituent of normal uranium. Furthermore, the deposit of uranium collected in the pocket 40 of the collector block 39 contains a considerably increased mount of U in view of the fact that it is not ordinarily feasible to separate U and U in the production of relatively large quantities of uranium enriched with U for commercial purposes. Accordingly, in this example the uranium deposited in the pocket 40 of the collector block 39 is considerably impoverished with respect to U as compared to natural or normal uranium.

In the operation of the calutron 10, it is highly desirable that a relatively intense stable beam of positive ions be projected by the ion accelerating structure 37, through the liner 44, toward the collector block 39; which operating condition requires that the source unit be productive of a steady and copious supply of positive ions. To accomplish this end in the source unit 20, the are discharges within the cavity in the arc-block 22 must be both relatively intense and uniform. Moreover, it is desirable that such are discharges should be steady and free from both intensity and position variations in order that the ion source unit 20 be productive of a highly continuous, copious and uniform supply of positive ions. Furthermore, the ion source unit 20 should be so constructed and arranged that the parts thereof are subjected to minimum wear and erosion, whereby the unit has a long life and an efiicient operating characteristic. An improved ion source unit embodying the features of the present invention provides a stable beam of positive ions of increased intensity by producing two stable and intense collinear arcs along the magnetic field, and thus effectively produces a uniform and intense arc discharge of increased length.

Referring now more particularly to Figs. 4 to 6, inclusive, of the drawings, there are illustrated the structural details of the calutron ion source unit 20 which is arranged in the magnetic field between the pole pieces of the calutron 10 in the manner previously explained, the ion source unit 20 comprising a charge receptacle 21 and an arc-block 22. The charge receptacle 21 comprises wall structure, including a removable cover 61, defining an upstanding cylindrical cavity 62 therein, that is adapted to receive a removable cylindrical charge bottle 63 containing a charge 64 which is to be vaporized. The areblock 22 comprises wall structure defining an upstanding vapor distributing chamber 65 and an upstanding arc chamber 66 therein, the cavity 62 communicating with the vapor distributing chamber 65 through a tubular member 67 supported by the wall structure of the charge receptacle 21 and the wall structure of the arc-block 22.

The wall structure of the charge receptacle 21 carries an exteriorly arranged electric heater 23 of any suitable form, whereby the charge receptacle 21 and consequently the charge bottle 63 may be appropriately heated in order to vaporize the charge 64 contained in the charge bottle 63. Similarly, the wall structure of the are-block 22 carries an exteriorly arranged electric heater 68 of any suitable form, whereby the arc-block 22, and more particularly the vapor distributing chamber 65 therein, may be heated in order to prevent condensation of the contained vapor, as explained more fully hereinafter.

More particularly, the wall structure of the arc-block 22 comprises a rectangular-shaped frame member 70, supporting an upstanding baffie plate 71, the frame mem ber 70 and the baffie plate 71 being formed of carbon or graphite. The frame member 70 is secured to the wall structure of the arc-block 22 by four upstanding strips 72, and comprises a top wall 73, a bottom wall 74, two upstanding. substantially parallel spaced-apart side walls 75, and a front wall 76, the front wall 76 having centrally disposed longitudinal slots 24a and 24b formed therein and communicating with the are chamber 66. The side edges of the baffie plate 71 are spaced a short distance from the side walls of the frame member 70 in order to provide communicating channels between the vapor distributing chamber 65 and the arc chamber 66 on each vertical side of the bafile plate. The rectangular frame member 70 and the baffle plate 71 are supported in the are-block 22 by means of the upper and lower end plates 80 of the wall structure of the arc-block 22.

The wall structure of the charge receptacle 21 carries a standard 81 which supports the cathode structure in cooperating relationship with respect to the arc-block. The cathode structure comprises a tubular arm 82 carrying a pair of heavy current conductors 83 and 84 insulated from each other by insulation strips 87 and connected to a pair of horizontal arms 85 and 86, the ends thereof separated by an insulating strip 87a. The horizontal arms 85 and 86 are secured to the conductors 83 and 84 respectively by screws and extend parallel to the front wall 76 of the arc-block 22. Two depending arms 88 and 89 are secured respectively to the ends of the transversely extending arms 85 and 86 on opposite sides of the arcblock 22, and two horizontal inwardly extending arms 90 and 91 are secured to the lower ends of the depending arms 88 and 89 respectively. The two inwardly extend- "ing arms 90 and 91 extend through two slots 92 and 93.

respectively, cut through the front wall 76 and through portions of the side walls 75 of the frame member 70. The inner ends of the inwardly extending arms 90 and 91 provide terminals for rigidly holding the filamentary cathode 25. The arms 85, 88, and 90, provide electrical connection between one conductor 83 and one end of the filamentary cathode 25; and the arms 86-, 89, and 91 provide electrical connection between the other conductor 84 and the other end of the filamentary cathode 25. The opposite ends of the filamentary cathode 25 are removably clamped in place by the respective terminals formed in the inward ends of the inwardly extending arms 90 and 91, these two terminals being connected to a suitable source of filament supply, as previously noted. It will be noted that the arms 85, 86, 88, 89, 90, and 91 of the cathode support structure lie in a plane parallel to the face of the front wall 76 of the arc-block 22, the median plane through the support structure mentioned and the axis of the filament passing through the arc chamber 66 a short distance from the interior surface of the front wall 76.

Supported in a transverse slot through the front wall 76 and through portions of the side walls 75 of the frame member 70 is a collimating electrode structure 94 corresponding to the aperture electrodes 29 and 30 of Fig. 3. The collimating electrode structure 94 in this case is of U- shaped cross section in a plane parallel to the magnetic field and perpendicular to the front Wall 76 of the frame member '70. Small projections 9411 are provided on the corners of the top and bottom walls of the collimating electrode structure 94 and these projections fit into corresponding slots in the side walls 75 to retain the structure 94 in position. The collimating electrode structure is provided with an end wall 95 between the filament 25 and the baffie plate 71 and upper and lower walls 96 and 97 on opposite sides of the filament 25, the end wall 95 and the upper and lower walls 96 and 97 forming the collimating electrode structure being formed of tungsten, or molybdenum, or the like. The upper and lower walls 96 and 97 have transversely extending slots 98 and 99 formed therethrough, corresponding to slots 31 and 32 of Fig. 3, and communicating with upper and lower zones 46 and 47, respectively, of the arc chamber 66. The lengths of these two transversely extending slots are greater than the width of the slots 24a and 24b formed in the front wall 76 of the arc-block 22. Furthermore these two collimating slots 98 and 99 are substantially parallel to the filamentary cathode 25 above and below said cathode, as previously noted, and serve to coll-imate the electron beams projected from the filamentary cathode 255 in opposite directions along the magnetic field. The widths and lengths of the transverse slots 98 and 99 are respectively less than the width and length of the filamentary cathode 25 as hereinabove explained. Anodes 100 and 101 extending into the arc chamber 66 in alignment with the central portion of the filamentary cathode 25 and in alignment with the transverse slots 98 and 99 formed in the collimating electrode structure, are supported by the top and bottom walls 80 and attached thereto by suitable screws.

Brackets 182 and 103 are attached to the vertical cathode supporting bus bars 88 and 89, respectively, and to the sides of the arc-block 22 by suitable screws to hold these bus bars and the cathode 25 in fixed relation with respect to the collimating structure and particularly the collimating apertures 98 and 99. These brackets 102 and 103 are insulated from the arc-block 22 by suitable insulation bushings 104 and 105, respectively, of heat resistant material.

Considering now the detailed operation of the calutron ion source 20, when the electric circuit for the heater 23 is completed, the charge receptacle 21 and consequently the charge bottle 63 are heated, whereby the charge 64 is vaporized, filling the cavity 62 in the charge receptacle 21. The vapor passes through the tubular member 67 into the vapor distributing chamber 65, whereby this.

chamber is filled with the vapor. The vapor is evenly distributed in the vapor distributing chamber 65 and electron emissive; and when the arc supply circuit is completed between the filamentary cathode 25 and the arc-block 22, electrons are projected from the central portion of the filamentary cathode 25 toward the upper and lower walls of the collimating electrode structure 94. More particularly, some of these electrons pass through the transverse slots 98 and 99 formed in the upper and lower walls 96 and 97 of the collirnating electrode structure 94-, into the upper and lower zones 46 and 47, respectively, in the arc chamber 66. Accordingly, two collinear streams of electrons having ribbon-like configurations are projected into the two gas or vapor filled zones 46 and 47 in the arc chamber 66, whereby the gas or vapor in the zones 46 and 47 is ionized. Moreover, the width of the streams of electrons is greater than the width of the upstanding slots 24a and 24b formed in the front wall 76, whereby any vapor flowing through the arc chamber 66 and the slots 24a and 24b must traverse the electron streams and thus be subjected to their ionizing influence. Thus, two ribbon-like arcs are produced in the respective zones 46 and 47 at the upper and lower ends of the arc chamber 66. The positive ions produced in the zones mentioned are drawn through the upstanding slots 24a and 24b formed in the front wall 76 of the frame member 70 by the associated ion accelerating structure 37, whereby two beams of positive ions having a substantially ribbon-like configuration are projected through the accelerating electrode structure 37, there to merge and be projected as a single beam into the adjacent end of the associated liner 44 and directed toward the cooperating collector block 39, as hereinabove explained.

In view of the foregoing, it is apparent that there has been provided an improved calutron, as well as an improved ion source in which an arc discharge of effectively greater length and of uniform and stable character is produced.

While there has been described what is at present considered to be the preferred embodiment of the invention,

it will be understood that various modifications may be. made therein and it is intended to cover in the appended,

claims all such modifications as fall within the true spirit and scope of the invention.

'What is claimed is:

1. An ion source comprising a hollow arc-block, means for establishing a magnetic field through said arc-block, said arc-block having a region for receiving gas to be ionized and having at least one elongated slit in the wall thereof aligned with said magnetic field and communicating with said region, means for supplying gas to be ionized into said region through an opening in said areblock, gas ionizing means for producing a pair of collinear arc discharges in said region aligned with said magnetic field, and means for withdrawing ions from said region through said slit.

2. An ion source comprising a hollow arc-block, means for establishing a magnetic field through said arc-block, said arc-block having a region for receiving gas to be ionized and having an elongated slit in a wall thereof aligned with said magnetic field and communicating with said region, means for supplying gas to be ionized into said region through an opening in said arc-block, means for projecting two oppositely directed streams of elec-, trons aligned with said magnetic field into two. zones of said region. whereby gas in said zones is ionized, and means for withdrawing ions from said zones through said slit.

3. An ion source comprising a hollow arc-block, means for establishing a magnetic field through said arc-block, said arc-block having a region for receiving gas to be ionized and having an elongated slit in a wall thereof aligned with said magnetic field and communicating with said region, means for supplying gas to be ionized into said region through an opening in said arc-block, means for projecting a plurality of collinear streams of electrons aligned with said magnetic field into different zones of said region, whereby gas in said zones is ionized, and means for withdrawing ions from said zones through said slit.

4. An ion source comprising a hollow arc-block, means for establishing a magnetic field through said arc-block, said arc-block having a region for receiving gas to be ionized and having an elongated slit in a wall thereof aligned with said magnetic field and communicating with said region, means for supplying gas to be ionized into said region through an opening in said arc-block, a cathode located within said region, means for projecting electrons from said cathode in opposite directions along said magnetic field into two zones of said region, Whereby gas in said zones is ionized, and means for withdrawing ions from said zones through said slit.

5. An ion source comprising a hollow arc-block, means for establishing a magnetic field through said arc-block, said arc-block having a region for receiving gas to be ionized and having an elongated slit in a Wall thereof aligned with said magnetic field and communicating With said region, means for supplying gas to be ionized into said region through an opening in said arc-block, a cathode located within said region, means for projecting electrons from said cathode in opposite directions along said magnetic field into two zones of said region, whereby two are discharges are respectively produced in said two zones, two apertured electrodes respectively disposed on opposite sides of said cathode and adjacent thereto and defining the respective cross sections of said are dis-' charges, and means for withdrawing ions from said zones through said slit.

6. An ion source comprising means for establishing a magnetic field, structure defining a gaseous region located in said magnetic field, a cathode disposed within said region, a pair of anodes disposed on opposite sides of said cathode along a line parallel to said magnetic field, means for producing an arc discharge between said cathode and each of said anodes, and means for withdrawing ions from said region transversely of said magnetic field.

7. An ion source comprising means for establishing a magnetic field, structure defining a gaseous region located in said magnetic field, a cathode disposed Within said region, a pair of anodes disposed on opposite sides of said cathode along a line parallel to said magnetic field, means for producing an arc discharge between said cathode and each of said anodes, an apertured member disposed intermediate said cathode and said anodes and defining the cross sections of said are discharges, and means for withdrawing ions from said region transversely of said magnetic field.

8. Apparatus for producing ions of vaporizable material comprising a receptacle for the material, means for heating and vaporizing said material, an elongated vapor compartment, tubular means connecting said vapor compartment with said receptacle, an elongated arc chamber connected to said vapor compartment by channels extending substantially throughout the length of said elongated arc chamber so that said vaporized material is fed to said are chamber substantially uniformly throughout the length of said arc chamber, a cathode positioned in said arc chamber, a pair of anodes in said are chamber,

and sources of current supply for energizing said cathode and said anodes to produce collimated ribbon-like electron discharges from said cathode to said anodes to set up arcs through said vapor in said are chamber and ionize said vapor.

9. Apparatus for producing ions of a material comprising a receptacle for the material, means for heating and vaporizing said material, an elongated vapor compartment, tubular means connecting said vapor compartment with said receptacle, an elongated are chamber connected to said vapor compartment by channels extending substantially throughout the length of said elongated arc chamber so that said vaporized material is fed to said arc chamber substantially uniform throughout the length of said are chamber, a cathode positioned in said are chamber, a pair of anodes in said arc chamber, and a pair of apertured collimating electrodes, one of said apertured electrodes being between said cathode and one of said anodes and the other of said apertured electrodes being between said cathode and the other of said anodes, said apertured collimating electrodes having apertures proportioned with respect to said cathode to collimate the electrons from said cathode into ribbon-like beams projected into said are chamber for ionizing said vaporized material.

10. Apparatus for producing ions of vaporizable material comprising a receptacle for the material, means for heating and vaporizing said material, an elongated vapor compartment, tubular means connecting said vapor compartment With said receptacle, an elongated arc chamber connected to asid vapor compartment by channels extending substantially throughout the length of said elongated arc chamber so that said vaporized material is fed to said are chamber substantially uniformly throughout the length of said are chamber, said are chamber having slot means in the front thereof, a cathode positioned in said are chamber substantially midway between the top and the bottom thereof, a pair of anodes in said are chamber, one of said anodes being near the top and the other of said anodes being near the bottom of said are chamber, collimating electrode means above and below said cathode sources of current supply for energizing said cathode, collimating electrodes and said anodes to produce sheet-like electron discharges from said cathode to said anodes immediately behind said slot means to set up arcs through said vapor in said arc chamber and ionize said vapor, and means for drawing ions out of said slot means.

11. Apparatus for producing ions of a material comprising a receptacle for the material, a heating unit adapted to be electrically energized for vaporizing said material in said receptacle, an elongated box-like container, a bafile extending substantially over the length of said container for dividing said container into a rear vapor compartment and a front are compartment, tubular means for feeding vapor from said receptacle to said rear vapor compartment, said rear compartment being connected to said front are compartment by channels extending substantially throughout the length of said container along the sides of said bafiie so that vapor from said vapor com partment is fed to said front are compartment substantially uniformly throughout the length of said front arc compartment, and means for producing a pair of collimated ribbon-like electron beams in said front are compartment for ionizing the vapor fed into said front are compartment.

12. Apparatus for producing ions of a gaseous material comprising a receptacle for the gaseous material, an elongated box-like container, a baflle extending substantially over the length of said container for dividing said container into a rear compartment and a front are compart- 'ment, tubular means for feeding the gaseous material from said receptacle to said rear compartment, said rear compartment being connected to said front are compartment by channels extending substantially throughout the length of said container along the sides of said baffle so that gaseous material from said rear compartment is fed to said front are compartment substantially uniformly throughout the length of said front are compartment, and means for producing a pair of collimated ribbon-like electron beams in said front are compartment for ionizing the vapor fed into said front are compartment.

13. Apparatus for producing ions of vaporizable material comprising a receptacle for the material, a heating unit adapted to be electrically energized for vaporizing said material in said receptacle, an elongated box-like container, a bafile extending substantially over the length of said container for dividing said container into a rear vapor compartment and a front are compartment, tubular means for feeding vapor from said receptacle to said rear vapor compartment, said rear compartment being connected to said font arc compartment by channels extending substantially throughout the length of said container along the sides of said baffle so that vapor from said vapor compartment is fed to said front are compartment substan tially uniformly throughout the length of said front are compartment, and means for producing a pair of electron beams in said front are compartment for ionizing the vapor fed into said front are compartment, said last mentioned means comprising a cathode located in said are compartment substantially midway between the ends thereof, a housing for substantially enclosing said cathode, said housing having apertures in the sides thereof facing the ends of said are compartment for collimating the electrons from said cathode into beams, and anodes positioned substantially in the ends of said are compartment.

References Cited in the file of this patent UNITED STATES PATENTS 2,011,922 Von Wedel -2 Aug. 20, 1935 2,061,254 Rockwood Nov. 17, 1936 2,225,047 Harni'sh Dec. 17, 1940 2,244,672 Brett June 10, 1941 2,257,794 Garner Oct. 7, 1941 2,300,436 Skellett Nov. 3, 1942 2,355,658 Lawlor Aug. 15, 1944 2,373,151 Taylor Apr. 10, 1945 

